The human cornea is a multilayered structure, having five principal layers. Loss of sight caused by corneal damage or pathological changes is one of the most common ophthalmologic diseases.
In surgical treatment for ocular-surface diseases in which the cornea is covered with the conjunctival epithelium to cause haze, at the present time, corneal epithelium transplantation is carried out.
However, transplantation of a cornea not only has difficulties such as securing the source of donation, but immunological rejection often leads to failures in the transplantation. Accordingly, scientists have attempted to use animal corneas to treat corneal diseases in humans, including studies performed on the direct transplantation of animal corneas. However, such direct animal corneal transplantations were unsuccessful because of immunological rejection. Additional research on preparations of artificial corneas from animal corneas by low-temperature freezing and simple sterilization treatment were also unsuccessful because the elimination of antigens was not complete and the patients' bodies could not accept the transplants due to poor tissue compatibility.
Besides, another kind of artificial cornea material is made of monomers. However, the conventional process to make artificial cornea for producing silicon-containing materials typically fail to provide satisfactory yield and purity while retaining advantageous transparency and oxygen permeability.
Thus, there still remains a need for an effective artificial cornea that can be harvested from animal corneas.
On the other hand, man has attempted to correct and adapt his conditions to enjoy perfect vision, or to endow it with greater resources for centuries. Diverse instruments have been invented toward this end, including spectacles, magnifier, contact lens, etc. Contact lenses that exhibit high oxygen permeability are generally preferred for the health and comfort of the eye.
Generally, a contact lens material having oxygen permeability contains a silicone (meth)acrylate or silicone styrene as a main component, and other components, in order to impart contamination resistance, strength and the like, a monomer adjusted with each objective performance is selected as a copolymerizing component and polymerized.
However, since the structure and characteristic of a polymerization part of each monomer are different in the case of the copolymerization in a multi-component system, it was fundamentally difficult to favorably copolymerize them, and experience and know-how were entrusted in many cases. Therefore, very long time and labors are required in order to provide better copolymerization with excellent productivity and complete end products.
Therefore, it is desirable to provide another contact lens material that eliminates the aforesaid drawbacks.